To be specific, there's a range. Medium chain triglycerides are the best and can aid with weightless. Coconut oil and, low and behold, butter has good amounts of this. You can also buy it in pure form from amazon. Transfats: you might aswell just eat high carb if you're consuming these.

Interesting, MCTs are saturated fats.

Also, beware of cooking with oils that have a low smoke point - smoking oil means free radicals, which are no good.